How to generate an array of 256 distinct numbers

Question

I have this:

#include     
using namespace std;   
int main()
{
    int a[256];
    int b;
    int k;
    for (int i = 0; i < 256; i ++){
             


        

Answer 1

std::random_shuffle is the way to go, as previously mentioned, but just in case you don't want to use it (maybe using ANSI C instead of C++), here's a quick-and-dirty implementation:

#include 
#include 

#define SIZE 256

static inline void
swap(int *a, int *b) {
    // Don't swap them if they happen to be the same element 
    // in the array, otherwise it'd be zeroed out
    if (a != b) {
        *a ^= *b;
        *b ^= *a;
        *a ^= *b;
    }
}

int main(void)
{
    int A[SIZE], i;
    // Initialize array with sequential incrementing numbers
    for (i = 0; i < SIZE; ++i)
        A[i] = i;

    // Initialize random seed
    srand(time(NULL));

    // Swap every element of the array with another random element
    for (i = 0; i < SIZE; ++i)
        swap(&A[i], &A[rand() % SIZE]);

    return 0;
}